The present invention pertains to an apparatus and a method for fabricating pressboard product, and in particular, pressboard formed from a filler comprising primarily shredded paper coated with a thermoplastic material, with or without additional thermoplastic material
Papers coated with a thermoplastic material (poly-coated papers) are utilized in a variety of applications. In one such application, kraft paper is coated with polyethylene to create roll headers utilized in the paper manufacturing industry. However, the use of poly-coated paper invariably generates waste or scrap, typically as a result of cutting the desired final product from blanks of sheet stock. For example, the poly-coated roll headers are round and therefore leave a relatively large offal portion when cut from rectangular sheet stock. The disposal of such material has proven to be difficult, time consuming and/or expensive The polymer component largely prevents normal processing of the paper component since it causes plugging of drainage screens, among other things. The scrap paper and polymer may be treated as waste and hauled to a landfill or incinerator for proper disposal. However, landfill disposal is very expensive in terms of both hauling costs and landfill fees; and in many states certain regulatory agencies can prohibit disposal in a landfill and/or incineration of such a product.
Alternatively, the scrap paper may be recycled in the fabrication of a pressboard product. One such apparatus and process for producing pressboard from scrap poly-coated paper is disclosed in U.S. Pat. No. 3,718,536, issued Feb. 27, 1973 to Downs et al., and entitled COMPOSITE BOARD AND METHOD OF MANUFACTURE However, the method and apparatus disclosed by Downs et al. includes a mere pressing of the board elements together Further, the Downs et al. system involves only a batch processing of the scrap paper, and as such has an associated low output and high cost. Although the Downs et al. patent represents as a possibility that the composite board could be manufactured continuously (column 5, lines 31-42) no useful, operative and/or practical apparatus or method whatsoever is set forth for a continuous implementation.
Another apparatus and process for producing pressboard from shredded poly-coated paper is set forth in Applicant's U.S Pat. No. 4,810,445, issued Mar. 7, 1989. In this system, the pressboard is formed continuously by depositing shredded poly-coated paper onto a first web or sheet, heating the thermoplastic material to its softening point, placing a second web or sheet atop the poly-coated paper to thereby sandwich it between the two webs, and then utilizing pinch rolls to apply a pressing force to compress the elements together One difficulty in this regard is that of obtaining optimum bonding within the shredded material and of the shredded material to the webs, for strength of product and ability to score.